Prevention of season cracking of brass



Patented Mar. 25, 194i UNITED STATES PATENT OFFICE Cedric Arthur Vincent-Daviss and Harold L. Maxwell, Wilmington, Del., assignors to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporationof Delaware No Drawing. Application March 12, 1940,

Serial No, 323,634

9 Claims. ei. 91 ss) This invention relates to a method of inhibi-tphenols, thiocresols, dimercap'to benzenes, thicing corrosion and, more particularly, to preven-, naphtholes, benzyl mercaptans, methyl benzyl tion or inhibition of season cracking of brass armercaptans, cyclohexyl mercaptan; long chain ticles. alkyl mercaptans such as lauryl mercaptan, cetyl 3 Brass articles which have been formed by cold mercaptan and the like and the corresponding 5- working or ,which for other reasons have internal disulfides. We prefer to use mercapto benzostresses are subject to a phenomenon known as thiazole as it is readily available, being a common season cracking. After a period oftimewhich rubberaccelerator, and gives excellent results. may vary depending upon conditions and upon The present invention, is not restricted to the 0 .the amount of internal strain present in the use of cyanide for cleaning the brass articles. 19

brass articles, the brass develops cracks or 115- The organic sulfur compound may be applied to sures. Such season cracking may develop in any brass surface which has been cleaned by any cleaned brass articles in storage or shipment prior suitable process sufficiently to afford uniform ditouse or during use. rect contact between the brass surface and the An excellent method for cleaning oxide and S fur pound. In order to obtain the dwired other undesirable or unsightly impurities or deinhibition of Season Cracking. it iS ecessary only posits from the surface of brass articles consists to deposit on the brass surface a thin film of in washing them with a solution of alkali metal the sulfur compound. This may e done by any cyanide. It has, however, been found that brass conventional method; we prefento apply a solu- 9 articles thus washed in a cyanide solution genti n of the sulfur compound on the surface of 20 erally are more subject to season cracking than the brass and then evaporate off the solvent to th hi h hav b sh d by v ti nal leave a film of the sulfur compound thereon. A methods, such as acid pickling and soap and waconvenient method consists in immersing the ter treatments. 7 brass articles in a dilute aqueous solution of the 5 An object of the present invention is to prosulfur compound, for example, in a solution convide a method for inhibiting or preventing season taining 0.01 to 1% by Weight of mercapto benzocracking of brass articles. A further object is to 4511182016 thereafter dry e a s article. provide a mean-s for cleaning brass articles with ew he so on y app d y p cy-anide solutions and to produce cleaned brass brushin o ot er conventional method.

9 articles which have little or no tendency to dee Organic Sulfur p d y e ssolved velop season cracking. The present invention in ei aqueous or non-aqueous solventor disalso includes brass articles of manufacture pre- DerSed n a liquid S all rt to the brass pared by the herein described th d, surface as a suspension or emulsion. Also, var- As one method of practicing the present inious known film-forming substances may be invention we may clean cold worked brass articles, orporated with the sulfur compound n the qfor example, cold drawn brass articles, stampp s o ppl e to the S- f the ings, or the like in a solution of sodium cyanide brass s rf e has been cleaned h a yanide containing 0.1 to 5 ounces of sodium cyanide per Solution or other substance which tends to accelgallon. After the articles have been washed in r e ason racking, t e ya or other for- 3 the cyanide solution, while still wet, the brass sure n material should be substantially completely face is washed thoroughly with water by rinsing removed m e b as e ore app y g he oror spraying until cyanide is substantially comgenie s r o p un pletely removed. The brass articles then are e following examples illustrate the effect of wetted with a, solution of an organic sulfur c mercapto benzothiazole in inhibiting the season 5 pound of the type described hereinafter. The cra n of brass:

articles are then dried so as to leave a film of the p e I sulfur compound on the surfaces thereof.

The organic sulfur compounds which are suitable for practicing the present invention are the i mercapto aryl thiazoles, hydrocarbon mercaptans and their corresponding disulfides. Examples of these are: mercapto benzothiazole and its homologrggs such as the mercapto tolylthiazoles, mer- A Dipped in 2.7 aquoou S Mia f dum cyanide ca xylylthiazoles, mercapto ethylbenz othia- 0 1 i zoles, and mercapto naphthothiazoles; also uno B Dipped in 0.05% solution of mercapto benzothiazole.

Brass shotgun shell heads were divided into two lots of 15 each and the lots were given different treatments, as follows:

Lot Treatment in the air at room temperature.

The samples of both lots were drained and dried The samples then were stored in a moist atmosphere at a temperature of 120 F. forone month. The samples then were subjected to av standard mercury accelerated cracking test and examined for cracks. The following results were obtained:

. Percent Lot Treatment cracked A. Sodium cyanide I 93. 3

B"... Mercapto benzothiazcle None The above mentioned standard mercury cracking test was carried out as follows: The brass articles were etched, inside and out, with nitric acid applied for a period of 15 seconds. After rinsing in water, a 1% solution of nitric acid containing 1% of mercurous nitrate was placed in the inside of the shells for 15 seconds. The shells then were again rinsed with water, wiped off and examined under a microscope at c: magnification.

Example II A lot of .22 caliber brass cartridge shells, which had been subjected to a conventional soap and water cleaning were dipped in a 0.05% aqueous solution of mercapto benzothiazole and dried at room temperature. The shells then were stored in a laboratory dessicator over 1 ammonia solution for 48 hours. Another lot of the soap and water cleaned shells, not treated with mercapto benzothiazole,'were also stored 48 hours in a dessicator over 1% ammonia solution. Both lots then were subjected to the mercury cracking test described above, with the following results:

Percent Lot cracked Treatment Mercapto benzothiazole None Not treated Example III Percent Treatment k d Treated with mercapto benzothiaiole Not treated 5 Our invention makes possible the storage or use of cold drawn brass articles for over long periods of time without danger of excessive season cracking. The invention is useful for treating brass articles which are stored or used under condito season crack.

We claim:

1. A process for cleaning brass articles which comprises washing said articles in a solution of alkali metal cyanide, washing to remove cyanide from the brass surface and depositing on the washed brass surface an organic sulfur compound selected from the group consisting of mercapto aryl thiazoles, hydrocarbon mercaptans and the corresponding disulfides.

2. A process for cleaning brass articles which comprises washing said articles in a solution of sodium cyanide, washing to remove cyanide from the brass surface, wetting the washed brass surface with a solution of an organic sulfur compound selected from the group consisting of mercapto aryl thiazoles, hydrocarbon mercaptans and the corresponding disulfides and drying to leave a film of said organic sulfur compound on said brass surface. I

' 3. A process for cleaning brass articles which comprises washing" said articles in a solution of sodium cyanide, washing to remove cyanide from the brass surface, wetting the washed brass surface with a solution of mercapto benzothiazole.

4. A process for cleaning brass articles which comprises washing said articles in a solution containing 0.1 to 5 ounces 'of sodium cyanide per gallon, washing to remove cyanide from' the brass surface, wetting the washed brass surface with a solution containing 0.01 to 1% by weight of mercapto benzothiazole and drying to leave a film of /mercapto benzothiazole on said surface.

5. The method for inhibiting season cracking of a brass article which comprises depositing an organic sulfur compound to the surface thereof.

6. The method for inhibiting season cracking of a brass article which comprises coating the surface thereof with mercapto benzothiazole.

7. The method for inhibiting season cracking of a brass article which comprises applying to the surface of said article a solution containing 0.01 to 1% by weight of mercapto benzothiazole and drying to leave a deposit of mercapto benzole on said surface.

8. A brass article which is resistant to season cracking, having deposited on the surface thereof an organic sulfur compound selected from the group consisting of mercapto aryl thiazoles, hydrocarbon mercaptans and the corresponding disulfides.

9. A brass article which is resistant to season cracking, having mercapto benzothiazole deposited on the surface thereof. 

